How I Make Rao's Legendary Lemon Chicken

INGREDIENTS
Base ingredients
1 small chicken - backbone removed and halved
4 teaspoons (12g) Diamond crystal kosher salt
3 tablespoons (45ml) olive oil
freshly ground black pepper - to taste
1 cup (240ml) low-sodium chicken stock
2 tablespoons (28g) unsalted cold butter - cubed
1/4 cup flat-leaf Italian parsley
4 lemon slices - for garnish
1 teaspoon lemon zest - for garnish, optional
Lemon sauce
1/2 cup (120ml) olive oil
1/3 cup (80ml) fresh lemon juice
1 tablespoon (15ml) red wine vinegar
5 cloves garlic - minced
1 tablespoon dried oregano
1 teaspoon Diamond crystal kosher salt
1/2 teaspoon freshly ground black pepper